1. Field of the Invention
This invention relates to a novel negative photoresist composition and to the method for providing photoresist layers. In particular the invention deals with N-benzyl acrylamide homopolymers and copolymers, and ultraviolet light sensitive negative photoresists that have good wetting properties on various substrates. The invention is particularly useful in that the photoresist compositions provided are sensitive to relatively shorter wavelengths of light, i.e., those that are sensitive in the deep ultraviolet light range of from about 200 nm to about 300 nm.
2. Description of the Prior Art
Photoresists are materials which change their solubility in response to a developer solution after the photoresist has been exposed, such as to ultraviolet radiation. Photoresist compositions may comprise a photosensitive compound, a film forming polymer and a solvent or in lieu of the photosensitizer and polymer, a polymer which is itself photosensitive may be used. As a consequence of the exposure to radiation of the photoresist, a different solubility rate results between the exposed and unexposed (masked over) portions of a resist film that yields a surface relief pattern after the development. Those photoresists which become more soluble in the exposed regions are referred to as "positive working" photoresists while those whose solubility is diminished by exposure to light are designated as "negative working" photoresists.
One of the limitations of materials currently used as commercial photoresists is their lack of sensitivity to light at wavelengths much below 300 nm. The resolution attainable with these resists is typically in the 2-4.mu. range and would be improved were they sensitive to shorter wavelengths of light. There is, therefore, a need for photoresist materials that are sensitive in the deep UV (200-300 nm) light range which permit higher resolution and thus a higher information density in the microcircuits manufactured using them. This sensitivity in the deep UV must be accompanied by the other normal attributes of a resist material including good adhesion to substrates, good contrast in images formed, and good etch resistance properties.